With the ever increasing demand for high speed communication, there has been a significant increase in the use of optics in computing systems. Semiconductor photonics, which can be implemented in an integrated circuit with known fabrication techniques, are increasingly deployed to meet the growing use of optics. The resulting semiconductor photodetectors have a small form factor, and their detection bandwidths can be very high. These traits make semiconductor photodetectors suitable for optical fiber based, high-speed telecommunication and datacenter interconnect applications.
However, in conventional photodetector designs, there is an inherent trade-off between responsivity and bandwidth. Traditionally, the responsivity is directly proportional to the path length that the light travels in the light absorption material (e.g., germanium). Considering a conventional normal incidence photodetector as an example, the thicker the absorption layer is, the higher the responsivity is. Unfortunately, a thicker absorption layer almost always features the drawback of longer carrier transit time that reduces the bandwidth of photodetectors.